Thursday, January 27, 2005

What is an Ion Drive?

"SMART-1's Ion Drive: From Fiction to Fact
By Bill Christensen

posted: 19 November 2004
06:43 am ET
SMART-1, the European Space Agency craft currently in orbit around the moon, makes use of a technology that was pure science fiction until the 1960s - the ion drive. An ion drive is a method of propulsion that uses electricity to create charged ions and then accelerate them with a magnetic field, pushing them out the rear of a spacecraft.

The ion drive was first described in 1947 by Jack Williamson in a short story published in Astounding Science Fiction called 'The Equalizer.' In the story, the spacecraft achieves a significant fraction of the speed of light, returning decades later due to time dilation.

George Lucas makes use of ion drives in Star Wars: the old Empire makes use of T.I.E. Fighters as small, manuverable spacecraft. T.I.E. is an acronym for Twin Ion Engines:

The hexagonal solar panels supply power to a unique propulsion system. Microparticle accelerators propel Ionized gasses at a substantial fraction of lightspeed...
(Read more about T.I.E. Fighters)

US astronaut Edward Gibson published Reach in 1989; this novel features a spacecraft with an ion drive that accelerates atoms of mercury to one percent of the speed of light before sending them out the rear of the craft.

SMART-1 has a stationary plasma thruster using xenon gas with 1190 watts of power available, giving a nominal thrust of 68 mN. The spacecraft contains 48 liters of xenon gas at 150 bar. The lifetime of the thruster is 7,000 hours at maximum power. The thrust is equivalent to two pennies resting in the palm of your hand.


SMART-1's Ion Drive

If this seems like a propulsion system that is a bit short of 'warp speed,' you're right. However, in the frictionless environment of space, even a gentle acceleration like this can produce real velocity if applied constantly over a long enough"

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